Process and apparatus for continuous liquid sampling

ABSTRACT

Clear samples of fluids containing solids suspended therein are continuously taken without filter-clogging using a filter apparatus immersed in the suspension comprising a rotatable filter disk divided by impermeable material into at least two sectors of liquid-porous material, in which the individual sectors are successively aligned, during each filter disk rotation cycle, in conduit relationship with both an afflux stream comprising liquid continuously withdrawn from the suspension and an efflux stream comprising the afflux stream after it has passed through a substantially closed cycle where the efflux stream passes through the sectors in a flow direction opposite to that of the afflux stream.

O United States Patent 1 1 3,618,767 [72] Inventor Gottfried Thummel [56] References Clted l N g; Y UNITED sures PATENTS gm m9 2.000.419 1/1931 Maclsaac 210/a2x [45] Patented 9 2,246,877 6/l94l Cunningham. 2l0l77X Am nee "Mu-k. cub" 2,446,364 8/l948 Demarest... 2l0/392 Munhfm Gem" 2,823,242 2/l958 McKay 2l0/334X [32] mm Nov 6 3, Y 2,909,031 0/1901 Filippinoetal... 21o/90x [33] Y 3,241,015 3/1900 Pashaian etal.... 210/17x [3n Hangs 3,490.879 1/1970 Urban 21o/324x Primary Examiner-John Adee Attorney-Burgess, Dinklage & Sprung ABSTRACT: Clear samples of fluids containing solids suspended therein are continuously taken without filter- [54] zr f fig gg FOR CONTINUOUS clogging using a filter apparatus immersed in the suspension 5 90 F comprising a rotatable filter disk divided by impermeable material into at least two sectors of liquid-porous material. in [52] US. Cl which the individual sectors are successively aligned, during [SI] Int. Cl [50] Field of Search 96,107, 324, 325, 333, 334, 365, 36

...................................................... 210/ 7, 210/82, 2 l0/96, 2l0/l86, 210/324, 2 l0/3 each filter disk rotation cycle, in conduit relationship with both an alt'lux stream comprising liquid continuously withdrawn from the suspension and an efflux stream comprising the afflux stream after it has passed through a substantially closed cycle where the efl'lux stream passes through the sectors in a flow direction opposite to that of the afllux stream.

PATENTEDNUV 9 ml SHEET 1 [IF 5 PATENTED 9 SHEET 3 [IF 5 FIG. 3

FIG. 4

INVIZNTOR. ow-FRIED Tn nn 51.

PROCESS AND APPARATUS FOR CONTINUOUS LIQUID SAMPLING The present invention is concerned with a method and an apparatus for the continuous taking of clear samples of fluids,

especially liquids, such samples being used, e.g., for the analytical monitoring and control of chemical and physical processes.

In many processes of the chemical art, especially in reactions of solids, crystallization processes, and reactions in which solid catalysts are used, it is necessary to control the process by a more or less frequent and regular taking of samples. The physical methods usually used today for the testing of the samples require the separation of the liquid from the solid phase, because in many cases only clear liquids can be tested without complication. Frequently practiced optical or chemical test methods which can be performed only with clear liquids are, for example, the measurement of optical rotation, circular dichroism, conductivity, pH value, and index of refraction, and colorimetric testing in visible, ultraviolet and infrared light as well as nuclear magnetic resonance spectroscopy and polarography.

In order to monitor rapidly evolving chemical processes and control them optimally on the basis of the results of such measurements, it is necessary to take samples continuously and analyze them almost instantaneously and without any delay.

For this purpose a large number of measuring apparatus have been developed, which use onstream-testing cells. The use of these apparatus is, however, restricted to clear liquids, since the solids suspended in liquids generally interfere with the methods of analysis employed. In order to take clear samples of liquid from such suspensions, discontinuously operating apparatus have been used exclusively hitherto, such as dip filters or filter candles, but these clog after a short length of time and have to be cleaned or replaced. Mechanical devices such as scrapers for cleaning filter surfaces represent nothing but makeshift aids, and they fail completely in the case of crystal mashes, because in this case additional crystals form in the filter pores and clog the filter.

It has now been found that, surprisingly, clear liquid samples can be taken from suspensions of solids, especially from crystal mashes, without any difficulty and in a fully continuous manner, by means of a filter apparatus immersed in the suspension, if a rotatable filter disk is used, which is divided by impermeable material into at least two sectors consisting of porous material, and in which the individual sectors are successively placed during each rotation both into the afflux and into the efflux of the continuously withdrawn and returned stream of liquid.

In the process according to the invention, liquid flows through each sector of the filter disk alternately from each side, i.e., a sector that has been partially clogged by the filtering action is automatically cleaned by the returning filtrate when the filter disk is turned. Under certain circumstances, a slight warming of the liquid specimen will prevent further crystallization in the meter and/or in the filter in the case of crystal mashes.

Basically, a number of embodiments of the apparatus, which is also a part of the invention, can be used for the performance of the process of the invention. For a better understanding of the present invention some typical embodiments are shown in the accompanying drawings in which:

FIG. 1 is a cross section through the simplest form of the apparatus according to the invention.

FIG. 2 is a cross section of a preferred embodiment.

FIGS. 3 and 4 are plane views of two difierent embodiments of the filter disk with separators, which can be incorporated in the apparatus of FIGS. 1 and 2.

FIG. 5 is a plane view of the masking plate 31 shown in FIG.

FIG. 6 is a plane view of the intermediate ring 24 shown in FIG. 2.

FIGS. 7 and 8 are cross-sectional views of preferred embodiments of the filter assemblies usable in apparatus according to FIGs. 2 (fixedly joined unit composed of filter disk and masking plate.)

FIG. 9 is a diagrammatic representation of a typical measuring system incorporating the invention which can be used to control processes.

The simplest embodiment of the apparatus of the invention shown in FIG. 1 consists of a housing I, an afi'lux line 2 and an efflux line 3, a seal 5 affixed to the housing 1 and provided with apertures 4 for the inflow and outflow, respectively, of the liquid specimens, and a cylindrical filter disk 6 which is rotatable about its central drive shaft 9. As shown in FIG. 3, the filter disk 6 is divided by impermeable separators 7 into a plurality of sectors 8 consisting of liquid porous material. It lies against the seal 5 in such a manner that each individual sector 8 is connected successively during each rotation both to the afilux line 2 and to the efi'lux line 3. The housing 1 consists of a steel tube (inside diameter 5 cm. for example) whose length (e.g., 3 m.) is governed by the design of the container holding the suspension to be sampled. The tube is closed at both ends by steel plates which are provided with apertures for the afflux line 2 and the efi'lux line 3 and for the central drive shaft 9. The more or less elastic seal 5 which abuts on housing 1, consists of a conventional sealing material, and is preferably equipped with tapered apertures 4 so as to increase the effective filtering area. The filter disk 6 consists of a sintered metal or other appropriate filter material, e.g., porcelain, and is divided by a plurality (six, in the case illustrated in FIGS. 3 and 4) of impermeable dividers 7 and 29 into the sectors 8 and 30. The filter disk 6 is mounted on and actuated by square drive means 13 extending from shaft 9 and is fastened thereon by nut 38. By means of the adjustable compression spring 10, the filter disk 6 is pressed against the seal 5 in such a manner that, on the one hand, an adequate seal is assured, and, on the other hand, the friction therebetween does not become excessive. The shaft cavity in the housing 1 is additionally provided with a sealing ring 12 to keep the liquid out of the housing cavity 11. The especially advantageous and proven embodiment of the apparatus of the invention shown in FIG. 2 difi'ers from the simpler type shown in FIG. I in the improved design of the filter assembly 27, and in the way in which the sealing means abutting against the housing is constructed. The filter assembly 27 consists of a porous filter disk 28 and a masking plate 31 affixed thereto, plane views of these two parts being given in FIGS. 4 and 5. The filter disk is divided by the impermeable steel dividers 29 into sectors 30 of equal size. The masking plate 31 is joined to the filter disk 28 by a matching annular sea 32 equipped with radial spokes in such a manner as to form separate shallow chambers 33. To seal this filter assembly 27 against the housing 1, an elastic gasket 22 is used, fitted therebelow with an intermediate ring 24 of polytetrafiuoroethylene that is only 0.5 to l mm. thick and which is shown separately in a plane view in FIG. 6. This intermediate ring 24 serves particularly to reduce the frictional resistance of the gasket 22, and it is provided with arcuate slots 25. In order to keep the gasket 22 and the intermediate ring 24 from turning, lateral lugs 26 are provided on the intermediate ring 24 and are locked into the housing I by means of bolts. The gasket 22 has cylindrical apertures 23 whose diameter is approximately the same as that of the afi'lux line 2 and the efflux line 3. Apertures 37 of the same size in the masking plate 31 lead down into the individual shallow chambers 33. The arcuate slots 25 in the intermediate ring 24 are of such a length that one or two apertures 37 are constantly in operative conduit alignment with affiux line 2, and one or two apertures are always in operative conduit alignment with efflux line 3.

Pressure variations and undesirable pulsation of the liquid fiow are prevented by this arrangement. The liquid in apertures 37 and chambers 33 results in a certain amount of mixing of the aspirated liquid with the liquid being discharged. This mixing is undesirable, since it results in certain errors of measurement. For this reason, the volume of aperture 37 and of chambers 33 is to be kept as small as possible. For the same reason, the apparatus according to the invention should be immersed in the flowing suspension of solids in such a manner that the liquid being discharged cannot immediately be reaspirated. For instance, if the liquid to be sampled is stirred and moves circularly in its vessel, the apparatus of this invention should be so immersed in said liquid that the moving stream of liquid impinges first on the aiflux line 2 of the apparatus to ensure continuous provision of fresh liquid thereto and to prevent aspiration of analyzed liquid from the efilux line 3 into afflux line 2.

Two additional embodiments of the filter assembly 27 are shown in FIGS. 7 and 8, and are designated as 27 and 27", respectively. In these embodiments the annular seal 32 is eliminated, since the filter disk 28 or 28" and the masking plate 31' or 31" are joined directly together with one another. The decision as to which type of filter assembly is to be given preference depends largely on the nature of the porous material and the dimensions of the entire filter assembly.

FIG. 9 illustrates the installation of the apparatus according to the invention designated by the overall reference numeral 14, in a typical monitoring and control system. Pump 21 pumps clear liquid separated from the mash 15 through the rotating filter assembly 27 driven by motor 16 and the affiux line 2 into a thermostat l7, and from there to the onstream test cell 18 of monitoring and control apparatus 19. Particularly in the case of crystal mashes it is advantageous to set the temperature of the thermostat somewhat higher than the temperature in the reaction vessel, because this prevents the formation of crystals in the test cell and in the lines running therefrom. if necessary, the liquid emerging from the test cell can be additionally heated in a heating coil such as 20, so as to assure that the filter disk segments will be washed out thoroughly by the liquid entering them from the efilux line 3.

The process according to the invention and the apparatus according to FIG. 2 are ideally suited for service in the racemate separation of a chloramphenicol intermediate. Utilizing the process and means according to the present invention, it is possible to take clear samples of liquid from suspensions of solids, especially crystal mashes, by using the filter apparatus according to the invention which avoids clogging of the filter disk by solid materials. It is, accordingly, possible to control reactions accompanied by crystallization or precipitation processes taking place in inorganic and organic liquids such as water, inorganic acids and bases, liquid ammonia or sulfur dioxide, aromatic or aliphatic hydrocarbons, halogenated hydrocarbons or organic acids or anhydrides such as for example, acetic acid or acetic anhydride, or organic bases such as for example, triethylamine or pyridine. In such processes solid material formation may be caused by precipitation effects due to the addition of reagents or merely by temperature control used to recrystallize dissolved compounds, which may merely have been added to the solvent or which may have originated during a chemical process taking place. On the other hand, the process and apparatus according to the present invention are especially useful in controlling catalyzed reactions in which solid catalysts are applied, as for instance, in hydrogenation, e.g. fluidized bed reactions using raney-nickel, raney-cobalt, noble metals as platinum or palladium or silver with or without inert carriers such as calcium carbonate, charcoal or alumina. The use of any other solid catalyst, such as for example ionexchange resins with specific acidic or basic properties is also within the scope of the present invention.

While the invention has been described specifically in relation to taking liquid sample streams from suspensions of filterable material in such liquid, it is to be understood that this invention is applicable as well to other fluids, for instance, gases, in which solid material is suspended or entrained. Accordingly, no unnecessary limitation should be implied from the foregoing specific description, as other embodiments of this invention will occur to those skilled in the art.

What is claimed is:

1. Process for taking a clear fluid sample stream from a suspension of filterable material in such fluid which process comprises filtering a fluid afflux stream withdrawn from said suspension through a rotating filter disk comprising at least two sectors consisting of material porous to said fluid which sectors are separated from each other by radial spokes of impermeable material and wherein said sectors during each rotation of said filter disk are successively moved into operative conduit alignment with said afflux stream and an efflux stream, respectively, said efflux stream comprising the afflux stream after it has passed through a substantially closed-cycle loop and passing through a sector in a flow direction opposite to the flow direction of the afflux stream passing through that section.

2. Process as claimed in claim 1 wherein said fluid is a liquid.

3. Process as claimed in claim 1 wherein said suspension is a crystal mash.

4. Process as claimed in claim 1 wherein said suspension consists of a liquid containing substantially insoluble solids.

5. Process as claimed in claim 4, wherein said solid is a catalytically efiective material.

6. Process as claimed in claim 2 wherein said liquid is an inorganic solvent.

7. Process as claimed in claim 2 wherein said liquid is an organic solvent.

8. Process for monitoring chemical processes occuring in a suspension comprising a solid suspended in a liquid which process comprises filtering a liquid afi'lux stream withdrawn from said suspension through a rotating filter disk comprising at least two sectors consisting of material porous to said liquid which sectors are separated from each other by radial spokes of impermeable material and wherein said sectors during each rotation of each filter disk are successively moved into operative conduit alignment with said afflux stream and an efflux stream, respectively, leading the resulting clear liquid sample stream to a measuring device, taking measurements of said clear liquid sample stream and returning said clear liquid sample stream as the efilux stream to said filter disk, wherein the efilux stream passes through a section of said filter disk in a flow direction opposite to the flow direction of the afflux stream passing through that section.

9. Process as claimed in claim 8 wherein said measurements are based on optical properties of said clear liquid.

10. Process as claimed in claim 8 wherein said measurements are based on chemical properties of said clear liquid.

11. Apparatus for taking a clear fluid sample stream from a suspension of filterable material in such fluid, which apparatus comprises a housing, an afflux line through which said sample stream is withdrawn from said suspension, an efflux line through which said sample stream is returned to said suspension, said afi'lux and efflux lines being disposed within said housing, a rotatable filter disk comprising at least two sectors consisting of material porous to said fluid which sectors are separated from each other by radial spokes of impermeable material, said filter disk being so disposed in said housing that said sectors, during each rotation of the filter disk about its axis, are successively moved into operative conduit alignment with the said afflux stream and efflux stream, respectively, so that the efflux stream passes through a section in a flow direction opposite to the flow direction of the afflux stream passing through that section, and means for rotating said filter disk about its axis.

12. Apparatus as claimed in claim 11 wherein said filter disk is disposed against a disk-shaped gasket affixed to said housing, said gasket having apertures communicating with said afflux and efi'lux lines, respectively and providing a continuous conduit between said lines and the filter disk sections.

13. Apparatus as claimed in claim 12 in which the apertures in said gasket taper outwardly toward the filter disk.

14. Apparatus as claimed in claim 11 wherein said filter disk is tightly joined with a disk-shaped masking plate fitted thereon and concentric therewith with a matching annular seal being disposed between said filter disk and said masking plate to form separated shallow chambers between said masking plate and said sectors, such shallow chambers communicating with said afilux and efi'lux lines through apertures in said masking plate.

15. Apparatus as claimed in claim 14 wherein said matching annular seal is made of polytetrafluoroethylene.

to said fluid which sectors are separated from each other by radial spokes of impermeable material, and a masking plate tightly fitted onto said filter disk and concentric therewith to form separate shallow chambers between said masking plate and said porous sectors wherein each of said shallow chambers opens to an orifice in said masking plate forming a conduit for removing and returning said clear fluid sample stream, said filter disk assembly having means for being rotated continuously about its axis.

I. i I i i 

2. Process as claimed in claim 1 wherein said fluid is a liquid.
 3. Process as claimed in claim 1 wherein said suspension is a crystal mash.
 4. Process as claimed in claim 1 wherein said suspension consists of a liquid containing substantially insoluble solids.
 5. Process as claimed in claim 4, wherein said solid is a catalytically effective material.
 6. Process as claimed in claim 2 wherein said liquid is an inorganic solvent.
 7. Process as claimed in claim 2 wherein said liquid is an organic solvent.
 8. Process for monitoring chemical processes occuring in a suspension comprising a solid suspended in a liquid which process comprises filtering a liquid afflux stream withdrawn from said suspension through a rotating filter disk comprising at least two sectors consisting of material porous to said liquid which sectors are separated from each other by radial spokes of impermeable material and wherein said sectors during each rotation of each filter disk are successively moved into operative conduit alignment with said afFlux stream and an efflux stream, respectively, leading the resulting clear liquid sample stream to a measuring device, taking measurements of said clear liquid sample stream and returning said clear liquid sample stream as the efflux stream to said filter disk, wherein the efflux stream passes through a section of said filter disk in a flow direction opposite to the flow direction of the afflux stream passing through that section.
 9. Process as claimed in claim 8 wherein said measurements are based on optical properties of said clear liquid.
 10. Process as claimed in claim 8 wherein said measurements are based on chemical properties of said clear liquid.
 11. Apparatus for taking a clear fluid sample stream from a suspension of filterable material in such fluid, which apparatus comprises a housing, an afflux line through which said sample stream is withdrawn from said suspension, an efflux line through which said sample stream is returned to said suspension, said afflux and efflux lines being disposed within said housing, a rotatable filter disk comprising at least two sectors consisting of material porous to said fluid which sectors are separated from each other by radial spokes of impermeable material, said filter disk being so disposed in said housing that said sectors, during each rotation of the filter disk about its axis, are successively moved into operative conduit alignment with the said afflux stream and efflux stream, respectively, so that the efflux stream passes through a section in a flow direction opposite to the flow direction of the afflux stream passing through that section, and means for rotating said filter disk about its axis.
 12. Apparatus as claimed in claim 11 wherein said filter disk is disposed against a disk-shaped gasket affixed to said housing, said gasket having apertures communicating with said afflux and efflux lines, respectively and providing a continuous conduit between said lines and the filter disk sections.
 13. Apparatus as claimed in claim 12 in which the apertures in said gasket taper outwardly toward the filter disk.
 14. Apparatus as claimed in claim 11 wherein said filter disk is tightly joined with a disk-shaped masking plate fitted thereon and concentric therewith with a matching annular seal being disposed between said filter disk and said masking plate to form separated shallow chambers between said masking plate and said sectors, such shallow chambers communicating with said afflux and efflux lines through apertures in said masking plate.
 15. Apparatus as claimed in claim 14 wherein said matching annular seal is made of polytetrafluoroethylene.
 16. Apparatus as claimed in claim 11 wherein said porous material is weldable sintered metal.
 17. Apparatus as claimed in claim 11 wherein said porous material consists of a ceramic or glass mass.
 18. Self-cleaning, nonclogging filter disk assembly adapted for use in closed-loop systems for taking a clear fluid sample stream from a suspension of filterable material in such fluid and returning said clear fluid sample stream to said suspension, which filter disk assembly comprises a rotatable filter disk having at least two sectors consisting of material porous to said fluid which sectors are separated from each other by radial spokes of impermeable material, and a masking plate tightly fitted onto said filter disk and concentric therewith to form separate shallow chambers between said masking plate and said porous sectors wherein each of said shallow chambers opens to an orifice in said masking plate forming a conduit for removing and returning said clear fluid sample stream, said filter disk assembly having means for being rotated continuously about its axis. 